There`s not a lot of information about climbing in Japan in English. Much of the information is only available in Japanese - or of course here on theCrag!

The Japan Free Climbing Association (http://freeclimb.jp/seibi/seibi.htm) is a good point of contact and there is a set of 5 guidebooks (all in Japanese) and an alpine guide book in English available covering all of Japan and its thousands of sport and trad routes and boulders.